1. Field of the Invention
The present invention relates to oscillators and specifically to coupling a common reference between two oscillator circuits.
2. Prior Art
In receiver circuits, it is common practice to buffer the crystal oscillator signal of a phase-locked loop (PLL) of a first receiver circuit and use the buffered version of the signal as the reference for the phase-locked loop (PLL) of a second receiver circuit. The buffer used is commonly a saturated amplifier with its output signal being almost a square wave. This square wave output has a high number of harmonics present and some of these harmonics can end up present in the band of the receiver or the band of the mixer's output. The transmission of the harmonic-rich signal between receivers over circuit board traces provides an opportunity for the signal to radiate. The harmonics of the buffered signal can be an interferer and detrimental to the system similar to unwanted signals picked up from the antenna.
FIG. 1 shows the prior art with the buffered oscillator signal being used as the reference for the second receiver circuit's PLL.